Front axle of a motor vehicle with steerable, driven or not driven wheels

ABSTRACT

A front axle of a motor vehicle with steerable, driven or not driven wheels on steering knuckles, which have been pivotably hinged at a wheel-guiding element with an upper and a lower bearing position, each of which with a pot-shaped sleeve with a sealed lubricant reservoir, accommodating a radial bearing for mounting a steering knuckle bolt and forming a bearing bushing, a stop disk, which absorbs axial forces and at which the roll bodies of the radial bearing are supported with the supporting surfaces, being disposed at the bottom of the sleeve.

[0001] The invention relates to a front axle of a motor vehicle withsteerable, driven or not driven wheels on steering knuckles, which havebeen pivotably hinged at a wheel-guiding element with an upper and alower bearing position, each of which with a pot-shaped sleeve with asealed lubricant reservoir, accommodating a radial bearing for mountinga steering knuckle bolt and forming a bearing bushing.

[0002] The invention also relates to a bearing bushing for a steeringknuckle mounting with a pot-shaped sleeve with a sealed lubricantreservoir, accommodating a radial bearing.

[0003] Front axles of this type are used in all-terrain vehicles, SUVs(Sport Utility Vehicles), light to heavy commercial vehicles and buses.The joint connection between the steering knuckle and the wheel-guidingelement, such as a rigid axle body or a guide of a single wheelsuspension, is realized in the case of known constructions by a king pinwith two bearing sites or by two separate steering knuckle bolts.Generally, needle bearings and needle bushings are used as a radialmounting. Axial forces are absorbed by a separate axial friction bearingor axial roller bearing. However, this bearing requires a particularlyreliable seal and this has turned out to be a weakness in practice. Thebearing must be lubricated at regular intervals in order to force thedirt, water and wear debris out of the mounting and to supply thebearing parts with fresh lubricating grease. If the seal fails, thedanger exists that the bearing will become unusable after a short time.

[0004] There have also already been attempts to make steering knucklebolt mountings, which do not require maintenance. For this purpose,relatively long and thin needle bearings are used, which produce highedge compressions under load. All known constructions furthermore havethe disadvantage that different components are required for the upperand lower bearing sites.

[0005] It is therefore an object of the invention to avoid thedisadvantages named and to create a front axle with a reliably sealedsteering knuckle mounting.

[0006] Pursuant to the invention, this objective is accomplished by afront axle of the initially mentioned type, which has, disposed at thebottom of the pot-shaped sleeve, a stop disk, which absorbs axial forcesand at which roll bodies of the radial bearing are supported with theirsupporting surfaces. The stop disk is in a position to support the rollbodies of the radial bearing at the front. A disk spring may be placedon the opposite front surface of the roll bodies, so that a constantaxial force presses the roll bodies against the stop disk and aligns itparallel to the axis.

[0007] In the case of the inventive front axle, a separate axial bearingmay be omitted and the axial forces, which arise, are transferredinstead directly over the stop disk to the steering knuckle bolt.

[0008] Pursuant to the invention, the roll bodies may be shorter andhave a larger diameter than the known mountings, so that high radialloads can be absorbed more elastically and reliably prevent distortionof the roll bodies.

[0009] The inventive front axle has the advantage that, because of theabsence of an axial bearing, the upper and lower bearing sites can beconstructed identically. This leads to a corresponding reduction in thediversity of the components of the components and to economic batchsizes.

[0010] The properties of the friction bearing are particularlyadvantages if the stop disk has a coating of polyvinylidene fluoride(PVDF) or consists thereof. This material enables relatively high forcesto be transferred by the roller supporting surfaces and has excellentlong-term behavior.

[0011] In a further development of the inventive concept, provisions canbe made so that the lubricant reservoir can alternatively be filled withgrease or oil. In both cases, it is filled by the manufacturer for thelifetime of the reservoir, so that the inventive front axle ispractically maintenance free. Preferably, it is filled with oil, fromwhich a longer lifetime can be expected and which is more effective thangrease. Nevertheless, the mounting of the inventive front axle isconstructed so that the supply lubricant, if necessary, can becontrolled and supplemented.

[0012] Pursuant to the invention, the bushing may have a sealing unit,which seals the mounting and comprises, preferably, a spring-loadedsealing element. The bearing is enclosed by the sealing unit, so thatdirt particles cannot penetrate into it from outside. It is well knownthat, in the course of time, seals are subjected to wear caused byrelative movements. However, because the sealing element isspring-loaded, a practically constant contacting force of the sealingelement can be achieved, so that the sealing unit seals reliably evenafter a prolonged period of use. Radial shaft sealing rings are suitableespecially when the lubricant reservoir is filled with oil. A seal withseveral lips can also be used, for reasons of costs, when the reservoiris filled with grease.

[0013] To facilitate the installation of the inventive front axle, thebushing can be preassembled with the radial bearing and the sealingunit. The bearing bushing can also be produced as a compact unit, readyto be installed, so that the installation, the maintenance, the costs aswell as the reliability of the mounting of the front axle are improved.

[0014] The inventive object is also accomplished by a bearing bushing ofthe type named above, for which, at the bottom of the pot-shapedbushing, a stop disk is disposed, which absorbs axial forces and at thefront side of which also the roll bodies of the radial bearing aresupported. A preferably spring-loaded disk spring may be placed on theroll bodies.

[0015] The stop disk advisably is coated with a friction bearingmaterial, preferably with polyvinylidene fluoride (PVDF), or consiststhereof. When the latter is lubricated slightly, it enables high forcesto be transferred and ensures reliable operation in the long run.

[0016] The inventive bearing bushing can be filled during its productionor installation with grease or oil for lifetime of the unit. Theinvention offers the possibility of filling the bushing with grease oroil, depending on the intended use, so that the area of application ofthe inventive bearing bushing is exceptionally large without requiringany changes in the components.

[0017] It has proven to be especially advantageous to use aspring-loaded sealing element, especially a radial shaft seal, assealing unit. If there is abrasive wear, the seal is continuouslyadjusted automatically, so that it does not leak, even after a prolongedperiod of use. This is the case particularly also for swiveling motionsand when centrifugal forces occur.

[0018] Further advantages and details of the invention arise out of thedescription of a particularly suitable example and from the Figures, ofwhich

[0019]FIG. 1 shows an inventive bearing bushing in a sectional view,

[0020]FIG. 2 shows an inventive bearing bushing with an insertedsteering knuckle bolt in a sectional view and

[0021]FIG. 3 shows the steering knuckle bolt mounting of an inventivefront axle in a partially sectional side view.

[0022] The bearing bushing 1, shown in section in FIG. 1, consists of aone-part pot-shaped sleeve 2, which is produced preferably by deepdrawing. A stop disk 3, the steel back 4 of which lies against the innerbottom 5 of the sleeve 2, is inserted in the sleeve 2. At its sideopposite to the bottom 5 of the sleeve 2, the stop disk 3 has a coating6 of a friction bearing material. In the example shown, a coating 6 ofpolyvinylidene fluoride (PVDF) is applied.

[0023] The mounting has a plurality of roll-shaped bodies 7, which areproduced from roller-bearing steel and are supported with their lateralroll bearing surfaces 8 on the PVDF coating 6 of the stop disk 3. Thebearing bushing 1 contains a total of 23 roller bodies 7, which areinserted, on the one hand, on the inside 9 of the sleeve 2 and, on theother, at the outside of a steering knuckle bolt, which is inserted inthe bearing bushing 1 and not shown in FIG. 1.

[0024] A lubricant 10 is applied at several places in the region of thestop disk 3 and the roll body 7.

[0025] A disk spring 12, which is fixed by a holding ring 13 having aninwardly 90° offset collar 14 so that the disk spring 12 is subjected atleast to a small prestressing force and the roll body 7 presses withapproximately constant force against the coating 6 even if wear occurs,acts on the roll supporting surface 11, which is opposite the rollsupporting surface 8. A clamping section 16 of a sealing ring 17 isclamped positively between the collar 14 of the holding ring 13, whichis offset 90° to the inside, and a locking ring 15, which is producedfrom a spring steel. The sealing ring 17 is produced from an elastomer,which may be an acrylonitrile/butadiene elastomer. The sealing ring 17is constructed as a radial shaft sealing ring and has a peripheral steelreinforcing ring 18. This reinforcing ring 18 exerts a radial pretensionon this section of the sealing ring 17, so that, in the installed state,the inner, protruding sealing edge 19 of the sealing ring 17 liesradially everywhere against the inserted steering knuckle bolt and theinterior of the bearing bushing 1 is sealed completely.

[0026] The sleeve 2 is sealed furthermore by a sealing ring 20, whichhas an approximately U-shaped cross section, which is offset twice by90°. In the interior of the sealing ring 20, there is acorrosion-protected, sheet steel reinforcement 21, which is coated by anelastomer 22 in the region of the sleeve opening. The outer section 23of the steel reinforcement 21, which extends parallel to thelongitudinal side of the sleeve 2, is bent towards the inside at its endand engages a peripheral groove 24 of sleeve 2. In the installed state,the steering knuckle bolt is in contact with the surface of the sealingring 20 having the coating 22 of elastomer, as well as with the sealingedge 19 of the sealing ring 17.

[0027]FIG. 2 shows the bearing bushing 1 of FIG. 1 with an insertedsteering knuckle bolt 25 in a sectional view. The steering knuckle bolt25 has a peripheral collar 26, which protrudes on the outside and liesaxially against the sealing ring 20. The sealing edge 19, which lieslaterally against the steering knuckle bolt 25, is also sealed radially.As can be seen in FIG. 2, the steering knuckle bolt 25 has a radiallysymmetrical cavity 27, adjoining one side of which there is a threadedborehole 28 and a radial recess 29, which forms a contacting surface fora plug 30, sealing the cavity 27. The cavity 27 serves as a lubricantreservoir, which can be filled with oil as well as grease. The side ofthe cavity 27 opposite the plug 30 tapers conically. Adjoining thisside, there is an opening 31, so that the lubricant, accommodated in thecavity 27, can reach the region of the bearing between the stop disk 3and the roller body 7. The steering knuckle mounting, shown in FIG. 2,is enclosed completely, so that a single filling with grease or oilsuffices for the whole of the service life. Due to the relative motionsbetween the steering knuckle bolt 25, the roll bodies 7 and the sleeve 2with the stop disk 3, the lubricating medium is distributedautomatically without requiring any control or refilling within thescope of maintenance. During the installation, the sealing lips and thesealing ring interstices of the sealing ring 17, 20 are greased, inorder to avoid penetration of dust, dirt or moisture also into thisregion.

[0028] Aside from the radial forces, which are absorbed by the mounting,there are also axial forces. These are passed over the sleeve bottom,the stop disk 3 and the steering knuckle bolt 25. An additional,separate axial bearing is therefore not required.

[0029]FIG. 3 shows the steering knuckle bolt mounting of a front axle ina partially sectional side view. The steerable wheels, which are notshown, are supported in each case at a steering knuckle 33, which isdivided fork-like in the region of the bearing. The steering knuckle 33is mounted pivotably at an upper bearing site 34 and a lower bearingsite 35 at a rigid axle housing 36, which is divided fork-like in thebearing area.

[0030] The upper bearing site 34 and the lower bearing site 35 each havea bushing 1 with an inserted steering knuckle bolt 25. The two bearingsites 34, 35, are symmetrical. The steering knuckle bolts 25 are pressedin each case into appropriate, mirror-image bearing seats 37 of the axlehousing 36. Similarly, the bearing bushing is pushed into a bearing set38 of a holding device 39 fastened to the steering knuckle 33.

[0031] List of Reference Symbols

[0032]1 bearing bushing

[0033]2 sleeve

[0034]3 stop disk

[0035]4 steel back

[0036]5 bottom of sleeve

[0037]6 PVDF coating

[0038]7 roll body

[0039]8 roll support surfaces

[0040]9 inner side of sleeve

[0041]10 lubricant

[0042]11 roll supporting surface

[0043]12 disk spring

[0044]13 holding ring

[0045]14 collar

[0046]15 locking ring

[0047]16 clamping section

[0048]17 sealing ring

[0049]18 reinforcing ring

[0050]19 sealing edge

[0051]20 sealing ring

[0052]21 steel reinforcement

[0053]22 elastomeric coating

[0054]23 outer section

[0055]24 groove

[0056]25 steering knuckle bolt

[0057]26 collar

[0058]27 cavity

[0059]28 threaded borehole

[0060]29 recess

[0061]30 plug

[0062]31 opening

[0063]32 front surface

[0064]33 steering knuckle

[0065]34 upper bearing site

[0066]35 lower bearing site

[0067]36 axle housing

[0068]37 accommodating opening

[0069]38 bearing seat

[0070]39 holding device

1. A front axle of a motor vehicle with steerable, driven or not drivenwheels on steering knuckles, which have been pivotably hinged at awheel-guiding element with an upper and a lower bearing position, eachof which with a pot-shaped sleeve with a sealed lubricant reservoir,accommodating a radial bearing for mounting a steering knuckle bolt andforming a bearing bushing, wherein a stop disk (3) which absorbs axialforces and at which the roll bodies (7) of the radial bearing aresupported with the supporting surfaces (8), are disposed at the bottomof the sleeve (2).
 2. The front axle of claim 1, wherein the stop disk(3) has a coating (6) of polyvinylidene fluoride (PVDF).
 3. The frontaxle of one of the preceding claims, wherein the lubricant reservoir(27) can be filled with grease or oil.
 4. The front axle of one of thepreceding claims, wherein a preferably pre-stressed disk spring (12) isplaced on supporting surfaces (11) of the roll body (7).
 5. The frontaxle of one of the preceding claims, wherein the bushing (1) has asealing unit, which seals the mounting.
 6. The front axle of claim 5,wherein the sealing unit preferably comprises a spring-stressed sealingelement.
 7. The front axle of claim 6, wherein the sealing elementcomprises a radial-shaft sealing ring (17).
 8. The front axle of one ofthe claims 5 to 7, wherein the bushing (1) can be pre-assembled with theradial bearing and the sealing unit.
 9. The front axle of one of thepreceding claims, wherein the axle is maintenance-free.
 10. The frontaxle of one of the preceding claims, wherein the radial bearing isconstructed in one or two rows.
 11. The front axle of one of thepreceding claims, wherein the upper and lower bearing sites (34, 35) areidentical.
 12. The bearing bushing for a steering knuckle mounting witha pot-shaped sleeve, accommodating a radial bearing and with a sealedlubricant reservoir, wherein, at the bottom of the sleeve (2), a stopdisk (3) is disposed, which absorbs axial forces and at which the rollbodies (7) of the radial bearing are supported with their supportingsurfaces (8).
 13. The bearing bushing of claim 12, wherein the stop disk(3) has a coating (6) of polyvinylidene fluoride (PVDF).
 14. The bearingbushing of claims 12 and 13, wherein the lubricant reservoir (27) can befilled with grease or oil.
 15. The bearing bushing of one of the claims12 to 14, wherein a preferably pre-tensioned disk spring (12) can beplaced on supporting surfaces (11) of the roll bodies (7).
 16. Thebearing bushing of one of the claims 12 to 15, wherein the bushing (1)has a sealing unit.
 17. The bearing bushing of claim 16, wherein thesealing unit comprises a spring-loaded sealing element.
 18. The bearingbushing of claim 17, wherein the sealing element comprises aradial-shaft sealing ring (17).
 19. The bearing bushing of one of theclaims 16 to 18, wherein the bushing can be pre-assembled with theradial bearing and the sealing unit.
 20. The bearing bushing of one ofthe claims 12 to 19, wherein the bushing is maintenance-free.
 21. Thebearing bushing of one of the claims 12 to 20, wherein the radialbearing is constructed in one or two rows.